In the past some tonearms have utilized a counterbalance weight in order to control downward or vertical stylus tracking force or have relied upon a combination of a counterbalance weight and a spring to govern this force.
Still others have utilized a combination of magnetic or electromagnetic force, together with a separate counterweight or counterweight and spring combination to control the stylus' vertical tracking force. Examples of the latter are disclosed in the U.S. Pat. Nos. 3,830,606 to Rabinow, 3,623,734 to Sakamoto et al., and the Britain Pat. No. 1,145,865 of 1969.
A problem with tonearms which utilize a counterweight is that this adds to the overall inertial mass of the tonearm. Such mass decreases the ability of the tonearm to change directions in response to unevenness in the horizontal grooved surface of a phonograph record. As a result, the stylus associated with the tone arm tends to gouge the high places in a record surface but fails, or has reduced ability, to track the low places with consequent loss of fidelity.
A tonearm which does not utilize a counterweight and therefore may tend to have a low inertial mass is disclosed in FIG. 5 of the Rabinow patent cited above. The tonearm disclosed is provided with a pneumatic tonearm pressure control. Such apparatus is complex and expensive to manufacture.
Some styli are flexibly attached to their cartridges by means of an elastomer or a spring metal member. Such styli move vertically in response to sound imparting ridges within the groove of a record and also follow slight vertical warpage in the horizontal surface of a record without appreciably affecting the vertical displacement of the associated cartridge and tonearm. In addition the stylus' downward tracking force may remain relatively constant during such slight vertical movement of the stylus.